Electroless plating method, electroless plating apparatus and storage medium

ABSTRACT

A multiple number of accurately-patterned metal layers can be formed on a substrate. On a substrate  11 , a patterned first metal layer  12  is formed (see FIG.  1 A), and then, a metal sacrificial layer  15  is formed on the first metal layer  12  (see FIG.  1 B). Further, an aqueous solution containing an ionized metal allowed to be substituted with a metal of the metal sacrificial layer  15  is coated on the metal sacrificial layer  15 , so that a catalyst layer  16  is formed on the metal sacrificial layer  15  (see FIG.  1 E) . Thereafter, a second metal layer  18  is formed on the catalyst layer  16  by performing an electroless plating process (see FIG.  1 F). Furthermore, the substrate  11  is etched by using the second metal layer  18  as a mask.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of Japanese Patent Application No. 2014-017694 filed on Jan. 31, 2014, the entire disclosures of which are incorporated herein by reference.

TECHNICAL FIELD

The embodiments described herein pertain generally to an electroless plating method and an electroless plating apparatus of forming an electroless plating layer on a substrate, and a storage medium therefor.

BACKGROUND

In an LSI (Large-Scale Integrated circuit) manufacturing process, a metal is grown on the entire surface of a substrate through the CVD or the PVD to be formed. In the past, patterning of the metal is performed by the etching with a chemical liquid or the dry-etching of Al wiring. Recently, the patterning of the metal is performed through a BEOL process in which an insulating layer is dry-etched, a wiring metal such as Cu is buried within a formed groove and then the metal is etched by the CMP (Patent Document 1).

In such a metal patterning process, a substrate is prepared first, and a multiple number of metal layers are formed on the substrate through the PVD or the CVD. Then, a resist pattern is formed on the multiple metal layers, and the multiple metal layers are etched with the resist pattern.

If the multiple metal layers are formed thickly on the metal and later dry-etched together, it takes a long time with a current dry-etching technique, so that a load of the etching process is increased. Further, depending on the kinds of the metal (for example, Cu), it is difficult to dry-etch the metal, and the metal cannot be etched accurately. As a result, it is very difficult to form, on the substrate, multiple metal layers which are patterned accurately.

Patent Document 1: Japanese Patent Laid-open Publication No. H11-297699

SUMMARY

In view of the foregoing problems, an example embodiment provides an electroless plating method and an electroless plating apparatus to be allowed to form an accurately-patterned metal layer on a substrate and, also to form, on the metal layer, a metal layer on which patterning by dry-etching does not need to be performed.

In one example embodiment, an electroless plating method performs an electroless plating process on a substrate on which a patterned first metal layer made of a metal compound which does not have catalytic property and a metal sacrificial layer are formed in sequence. The electroless plating method includes forming a catalyst layer on the metal sacrificial layer by coating, on the metal sacrificial layer, an aqueous solution containing an ionized metal allowed to be substituted with a metal of the metal sacrificial layer; and forming a second metal layer by performing the electroless plating process on the catalyst layer.

In another example embodiment, an electroless plating apparatus performs an electroless plating process on a substrate on which a patterned first metal layer made of a metal compound which does not have catalytic property and a metal sacrificial layer are formed in sequence. The electroless plating apparatus includes a catalyst layer forming unit configured to form a catalyst layer on the metal sacrificial layer by coating, on the metal sacrificial layer, an aqueous solution containing an ionized metal allowed to be substituted with a metal of the metal sacrificial layer; and a second metal layer forming unit configured to form a second metal layer by performing the electroless plating process on the catalyst layer.

In yet another example embodiment, a computer-readable storage medium has stored thereon computer-executable instructions that, in response to execution, cause an electroless plating apparatus to perform an electroless plating method of performing an electroless plating process on a substrate on which a patterned first metal layer made of a metal compound which does not have catalytic property and a metal sacrificial layer is formed in sequence. Further, the electroless plating method includes forming a catalyst layer on the metal sacrificial layer by coating, on the metal sacrificial layer, an aqueous solution containing an ionized metal allowed to be substituted with a metal of the metal sacrificial layer; and forming a second metal layer by performing the electroless plating process on the catalyst layer.

According to the example embodiment, it is possible to form a multiple number of accurately-patterned metal layers on a substrate easily and securely.

The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

In the detailed description that follows, embodiments are described as illustrations only since various changes and modifications will become apparent to those skilled in the art from the following detailed description. The use of the same reference numbers in different figures indicates similar or identical items.

FIG. 1A to FIG. 1G are diagrams illustrating a sequence of an electroless plating method in accordance with an example embodiment;

FIG. 2 is a block diagram illustrating an electroless plating apparatus in accordance with the example embodiment; and

FIG. 3A and FIG. 3B are diagrams illustrating a conventional method of forming multiple metal layers as a comparative example.

DETAILED DESCRIPTION

In the following detailed description, reference is made to the accompanying drawings, which form a part of the description. In the drawings, similar symbols typically identify similar components, unless context dictates otherwise. Furthermore, unless otherwise noted, the description of each successive drawing may reference features from one or more of the previous drawings to provide clearer context and a more substantive explanation of the current example embodiment. Still, the example embodiments described in the detailed description, drawings, and claims are not meant to be limiting. Other embodiments may be utilized, and other changes may be made, without departing from the spirit or scope of the subject matter presented herein. It will be readily understood that the aspects of the present disclosure, as generally described herein and illustrated in the drawings, may be arranged, substituted, combined, separated, and designed in a wide variety of different configurations, all of which are explicitly contemplated herein.

Hereinafter, example embodiments will be described with reference to FIG. 1A to FIG. 2.

A metal layer forming method in accordance with an example embodiment includes, as depicted in FIG. 1A to FIG. 1F, forming a first metal layer 12, a metal sacrificial layer 15, a catalyst layer 16 and a second metal layer 18 in sequence on a silicon substrate (hereinafter, simply referred to as “substrate”) 11 formed of a semiconductor wafer or the like. Here, a thickness of the whole metal layers including the first metal layer 12, the metal sacrificial layer 15, the catalyst layer 16 and the second metal layer 18 is set to be equal to a thickness of a metal layer including a first metal layer 12 and the second metal layer 18 of a comparative example to be described later, as depicted in FIG. 3A and FIG. 3B.

In this case, a substrate main body made of Si may be used as the substrate 11. Further, a structure having a substrate main body made of Si and a TEOS layer formed on the substrate main body may be used as the substrate 11.

Now, an electroless plating apparatus 30 configured to form the first metal layer 12, the metal sacrificial layer 15, the catalyst layer 16 and the second metal layer 18 on the substrate 11 will be explained with reference to FIG. 2.

The electroless plating apparatus 30 includes a first metal layer forming unit 31; a metal sacrificial layer forming unit 32; a catalyst layer forming unit 33; and a second metal layer forming unit 34. The first metal layer forming unit 31 is configured to form the first metal layer 12 made of a metal compound which does not have catalytic property on the substrate 11. The metal sacrificial layer forming unit 32 is configured to form the metal sacrificial layer 15 on the first metal layer 12. The catalyst layer forming unit 33 is configured to form the catalyst layer 16 on the metal sacrificial layer 15 by coating, on the metal sacrificial layer 15, an aqueous solution containing an ionized metal allowed to be substituted with a metal of the metal sacrificial layer 15. The second metal layer forming unit 34 is configured to form the second metal layer 18 by performing an electroless plating process on the catalyst layer 16.

Further, an etching unit 35 configured to perform an etching process on the substrate 11 with the second metal layer 18 as a mask to perform a patterning process on the substrate 11 is provided at the rear end of the catalyst layer forming unit 33 and the second metal layer forming unit 34.

Operations of the individual components of the above-described electroless plating apparatus 30, i.e., the first metal layer forming unit 31, the metal sacrificial layer forming unit 32, the catalyst layer forming unit 33, the second metal layer forming unit 34 and the etching unit 35 are controlled by a controller 40 according to various kinds of programs recorded in a storage medium 41 provided in the controller 40, so that various processes are performed on the substrate 11. Here, the storage medium 41 stores thereon various kinds of setup data or various kinds of programs such as a metal layer forming program to be described later. Here, the storage medium 41 may be implemented by a computer-readable memory such as a ROM or a RAM, or a disk-type storage medium such as a hard disk, a CD-ROM, a DVD-ROM or a flexible disk, as commonly known in the art.

Now, an operation of the example embodiment having the above-described configuration will be discussed with reference to FIG. 1A to FIG. 1G.

First, the substrate 11 formed of a semiconductor wafer or the like is transferred into the electroless plating apparatus 30.

Here, the substrate 11 may have a planar surface (see FIG. 1A), or may have thereon a recess.

As a way to form the recess on the substrate 11, a commonly known conventional method may be appropriately employed. To elaborate, a general-purpose technique using a fluorine-based gas or a chlorine-based gas may be used as a dry-etching technique, for example. Especially, to form a hole having a high aspect ratio (ratio of a depth of the hole to a diameter of the hole), a method using ICP-RIE (Inductively Coupled Plasma Reactive Ion Etching) configured to perform a high-speed deep-hole etching may be more appropriately utilized. Particularly, a method called Bosch process, in which an etching process using sulfur hexafluoride (SF₆) and a protection process using a Teflon (registered trademark)-based gas such as C₄F₈ are performed repeatedly, may be appropriately employed.

Then, in the electroless plating apparatus 30, the substrate 11 is loaded into the first metal layer forming unit 31. In this first metal layer forming unit 31, the patterned first metal layer 12 is formed on the substrate 11.

To elaborate, as depicted in FIG. 1A, the first metal layer 12 made of TiN or TaN is formed on the substrate 11 by the CVD or the PVD. Here, the TiN or TaN is formed of a metal compound which does not have the catalytic property for a second metal layer 18 to be formed by the electroless plating process, as will be described later.

Subsequently, the substrate 11 having thereon the first metal layer 12 formed thereon is sent into the metal sacrificial layer forming unit 32. In this metal sacrificial layer forming unit 32, the metal sacrificial layer 15 is formed on the first metal layer 12 (see FIG. 1B).

The metal sacrificial layer 15 contains a metal allowed to be substituted with a metal forming the catalyst layer 16 to be described later. The metal sacrificial layer 15 is formed on the first metal layer 12 by the CVD or the PVD in the metal sacrificial layer forming unit 32.

Further, the metal sacrificial layer 15 may be formed on the first metal layer 12 as a continuous film to have a thickness smaller than that of the first metal layer 12, or may be formed on the first metal layer 12 as a discontinuous film. Furthermore, the metal sacrificial layer 15 may be formed in a particulate shape. A thickness of a metal layer formed of the first metal layer 12 and the metal sacrificial layer 15 is set to be smaller than a thickness of a metal layer formed of the first metal layer 12 and the second metal layer 18 in the prior art shown in FIG. 3A and FIG. 3B.

Afterwards, a resist pattern 13 is formed on the first metal layer 12 and the metal sacrificial layer 15. Then, by performing the etching process on the first metal layer 12 and the metal sacrificial layer 15 on which the resist pattern 13 is formed, the first metal layer 12 and the metal sacrificial layer 15 are patterned (see FIG. 1C). Thereafter, the resist pattern 13 is removed from the first metal layer 12 and the metal sacrificial layer 15 (see FIG. 1D).

One of Ti, W, Cu, Ni and Co may be used as a metal that forms the metal sacrificial layer 15.

Subsequently, the substrate 11, in which the metal sacrificial layer 15 is formed on the first metal layer 12, is sent into the catalyst layer forming unit 33. In the catalyst layer forming unit 33, an aqueous solution containing an ionized metal allowed to be substituted with the metal of the metal sacrificial layer 15 is coated on the metal sacrificial layer 15 on the substrate 11, so that the catalyst layer 16 is formed on the metal sacrificial layer 15 (see FIG. 1E).

To elaborate, in case that the metal sacrificial layer 15 is made of Ti or W, an aqueous solution such as palladium (Pd) chloride solution or palladium (Pd) sulfate solution is coated on the metal sacrificial layer 15. In this case, Ti or W of the metal sacrificial layer 15 is substituted with Pd ions in the aqueous solution, so that the Pd ions are precipitated on the metal sacrificial layer 15.

Accordingly, the catalyst layer 16 made of any one of Pd, Au and Pt can be formed on the metal sacrificial layer 15.

Thereafter, the substrate 11 having thereon the catalyst layer 16 is sent to the second metal layer forming unit 34. In this second metal layer forming unit 34, the electroless plating process is performed on the substrate 11, so that the second metal layer 18 is formed.

To be specific, by performing the electroless plating process of a Ni metal on the substrate 11, the plating process in which the Pd metal of the catalyst layer 16 is used as a catalyst is performed on the substrate 11, so that, the second metal layer 18 made of the Ni metal is formed on the catalyst layer 16 (see FIG. 1F).

At this time, the second metal layer 18 formed through the electroless plating process is set to have a thickness substantially same to the thickness of the metal layer formed of the first metal layer 12 and the second metal layer 18 of a comparative example in FIG. 3A and FIG. 3B. The second metal layer 18 of the present example embodiment is selectively formed only on the patterned metal layer.

Further, in the second metal layer forming unit 34, the electroless plating process may be performed by using a Cu metal instead of the Ni metal. In such a case, the second metal layer 18 made of the Cu metal may be formed on the catalyst layer 16.

Thereafter, the substrate 11 having thereon the second metal layer 18 is sent to the etching unit 35. In this etching unit 35, the etching process is performed on the substrate 11 with the second metal layer 18 as a mask (see FIG. 1G).

In accordance with the present example embodiment, after the first metal layer 12 and the metal sacrificial layer 15 are formed on the substrate 2, the first metal layer 12 and the metal sacrificial layer 15 are etched by using the resist pattern 13. Then, the catalyst layer 16 is formed on the first metal layer 12 and the metal sacrificial layer 15 which are patterned. Then, by performing the electroless plating process with the catalyst layer 16, the second metal layer 18 is formed. Accordingly, since the thin metal layer formed of the first metal layer 12 and the metal sacrificial layer 15 can be dry-etched with the resist pattern 13, a load of the etching process can be reduced, so that it is possible to obtain the first metal layer 12 and the second metal layer 18 which are patterned accurately. Furthermore, as compared to a case that a metal layer is formed on the entire surface of the substrate 11 through the CVD or the PVD, the second metal layer 18 can be selectively formed only on the patterned first metal layer 12 and metal sacrificial layer 15 with the catalyst layer 16 therebetween.

Now, a comparative example will be explained with reference to FIG. 3A and FIG. 3B. As depicted in FIG. 3A and FIG. 3B, when forming multiple metal layers on a substrate 11, a first metal layer 12 made of TiN or TaN and a second metal layer 18 made of Ni are formed on the substrate 11 through the CVD or the PVD, and, then, a resist pattern 23 is formed on the second metal layer 18. Then, by performing an etching process with the resist pattern 23, the first metal layer 12 and the second metal layer 18 are patterned.

In FIG. 3A and FIG. 3B, since the thick metal layer formed of the first metal layer 12 and the second metal layer 18 on the substrate 11 needs to be etched together, it takes a long time with the current dry-etching technique, so that a load of the etching process is increased. As a result, it is difficult to form the first metal layer 12 and the second metal layer 18 which are patterned accurately.

In contrast, in accordance with the example embodiment, a load of the etching process can be reduced, and it is possible to obtain the first metal layer 12 and the second metal layer 18 which are patterned accurately.

Further, in the present example embodiment, the second metal layer 18 is used as a mask for etching the substrate 11. However, the example embodiment is not limited thereto, and the second metal layer 18 may be used as a wiring of a device by being formed to have a required thickness.

From the foregoing, it will be appreciated that various embodiments of the present disclosure have been described herein for purposes of illustration, and that various modifications may be made without departing from the scope and spirit of the present disclosure. Accordingly, the various embodiments disclosed herein are not intended to be limiting, with the true scope and spirit being indicated by the following claims. 

We claim:
 1. An electroless plating method of performing an electroless plating process on a substrate on which a patterned first metal layer made of a metal compound which does not have catalytic property and a metal sacrificial layer are formed in sequence, the electroless plating method comprising: forming a catalyst layer on the metal sacrificial layer by coating, on the metal sacrificial layer, an aqueous solution containing an ionized metal allowed to be substituted with a metal of the metal sacrificial layer; and forming a second metal layer by performing the electroless plating process on the catalyst layer.
 2. The electroless plating method of claim 1, further comprising: forming the patterned first metal layer formed of the metal compound which does not have the catalytic property on the substrate before the forming of the catalyst layer; and forming the metal sacrificial layer on the first metal layer.
 3. The electroless plating method of claim 1, wherein the metal compound of the first metal layer is formed of TiN or TaN.
 4. The electroless plating method of claim 1, wherein the metal of the metal sacrificial layer is formed of Ti, W, Cu, Ni or Co.
 5. The electroless plating method of claim 1, wherein a metal of the catalyst layer is formed of Pd, Au or Pt.
 6. The electrodes plating method of claim 1, wherein the second metal layer is formed of an electroless plating layer of Ni.
 7. An electroless plating apparatus that performs an electroless plating process on a substrate on which a patterned first metal layer made of a metal compound which does not have catalytic property and a metal sacrificial layer are formed in sequence, the electroless plating apparatus comprising: a catalyst layer forming unit configured to form a catalyst layer on the metal sacrificial layer by coating, on the metal sacrificial layer, an aqueous solution containing an ionized metal allowed to be substituted with a metal of the metal sacrificial layer; and a second metal layer forming unit configured to form a second metal layer by performing the electroless plating process on the catalyst layer.
 8. The electroless plating apparatus of claim 7, further comprising: a first metal layer forming unit configured to form the patterned first metal layer formed of the metal compound which does not have the catalytic property on the substrate before forming the catalyst layer; and a metal sacrificial layer forming unit configured to form the metal sacrificial layer on the first metal layer.
 9. The electroless plating apparatus of claim 7, wherein the metal compound of the first metal layer is formed of TiN or TaN.
 10. The electroless plating apparatus of claim 7, wherein the metal of the metal sacrificial layer is formed of Ti, W, Cu, Ni or Co.
 11. The electroless plating apparatus of claim 7, wherein a metal of the catalyst layer is formed of Pd, Au or Pt.
 12. The electrodes plating apparatus of claim 7, wherein the second metal layer is formed of an electroless plating layer of Ni.
 13. A computer-readable storage medium having stored thereon computer-executable instructions that, in response to execution, cause an electroless plating apparatus to perform an electroless plating method of performing an electroless plating process on a substrate on which a patterned first metal layer made of a metal compound which does not have catalytic property and a metal sacrificial layer is formed in sequence, wherein the electroless plating method comprises: forming a catalyst layer on the metal sacrificial layer by coating, on the metal sacrificial layer, an aqueous solution containing an ionized metal allowed to be substituted with a metal of the metal sacrificial layer; and forming a second metal layer by performing the electroless plating process on the catalyst layer. 